Evaluation of the Ti diffusion process during fabrication of Ti:LiNbO3 optical waveguides

The Ti oxidation and the formation of a surface Ti-Nb-O compound occurring during Ti diffusion process in LiNbO₃ for fabricating optical waveguides have been analysed using backscattering spectrometry and glancing-angle X-ray diffraction. Results show that Ti oxidation partially occurs owing to Ti reaction with oxygen atoms of the substrate and that the Ti-Nb-O compound grows epitaxially and behaves as a real source for Ti diffusion.     

Influence of channeling effects on ion distribution and damage profiles during high energy ion implantation in Si

Nitrogen implantation has been performed in silicon [001] crystals in carefully controlled alignment conditions. The channeling effects are clearly evident when implanting in [001] and [011] directions at energies ranging from 0.6 to 1.4 MeV. Both ion distribution and damage profiles are strongly influenced by channeling effects during ion implantation. The angular region around the [001] direction has been also investigated by implanting at small angles with respect to the axis. The same kind of study has been performed by implanting at different angles with respect to the planar (011) direction. The ion distributions (investigated by SIMS) show a strong dependence upon the alignment conditions. Moreover in high energy ion implantation, the lattice damage is located deep inside the crystal, leaving the surface layer almost unperturbed. The channeling effects on the damage production have been investigated by double crystal diffraction (DCD) in the low-dose regime and by RBS-channeling experiments (after implantation at doses greater than 1 × 10¹⁵ cm^–2) and for different ion alignment conditions.A big increase in the ion ranges and a strong reduction in the lattice damage is evident when implanting along major crystal axes. No saturatíon of the lattice damage and of the channelled component of the beam has been detected if the implantation is performed parallel to the [011] axis.     

Atom location in complex lattices: Pb in α-Al2O3

The channeling technique has been used to locate Pb implanted into α-Al₂O₃ single crystal. The main purpose has been to learn how to obtain information about the location of an impurity in a complex structure. A Pb location is proposed according to data of full angular scans through different axial and planar channeling dips.     

Sodium surface concentration analysis on glass by 23Na(p,α)20Ne nuclear reaction

The ²³Na(p, α)²⁰Ne nuclear reaction has been used to investigate the depth profile of Na near the surface of commercial soda-lime-silicate glasses. The depth profile of Na has been quantitatively determined (with a depth resolution of about 120 Å) without migration effects due to the measurement method. Such perturbations, which make other analysis techniques difficult to use, appear only with very high current densities of the incident beam. A brief review of the principles of nuclear reaction used to analyse the concentration profile near the surface of samples is presented. A comparison with the traditional methods is discussed.     

Surface and interface analysis of titanium nitride diffusion barriers

Titanium nitride films were produced on silicon substrate by ion beam assisted deposition in the alternate mode: first, thin titanium layers were deposited by electron beam evaporation and then titanium nitride was formed by nitrogen implantation at room temperature; this cycle was then iterated many times in order to obtain thicker titanium nitride layers. The obtained films were characterized with respect to atomic composition by Rutherford backscattering spectrometry and nuclear reaction analysis techniques, while chemical bonding was investigated by Auger line-shape analysis. We observe that nitrogen implantation, along with the production of titanium nitride, induces silicon migration into the film. Silicon transport is connected to point defects produced by ion implantation as well as by chemical driving forces associated with silicides formation.     

Shallow donors and deep levels in GaAs grown by atomic layer molecular beam epitaxy

We correlate the Si concentration measured by secondary ion mass spectrometry (SIMS) and the net donor concentration in GaAs:Si grown by atomic layer molecular beam epitaxy (ALMBE); Si was supplied during: (a) both the As and the Ga subcycles, (b) the As subcycle, and (c) the Ga subcycle; the layers were grown at temperatures in the 300-530°C range. The results show that Si incorporation and its compensation depend on the Si-supply scheme and that the extent of compensation decreases with the growth temperature. We also study the deep levels in the ALMBE GaAs grown under the above conditions. Our results show the occurrence of M1, M3 and M4 levels with concentrations that are: (i) essentially independent of both the Si supply scheme and the ALMBE growth temperature, (ii) close to those of MBE GaAs grown at 600°C, and (iii) up to 2 orders of magnitude lower than that of GaAs prepared by molecular beam epitaxy (MBE) at similar temperatures.